This invention relates generally to fuel filters employed in connection with internal combustion engines. More particularly, the present invention relates to fuel filters and lubricating oil filters having a replaceable cartridge for removing foreign particles and/or separating water from the fuel supply or oil system of an internal combustion engine. The cartridge is secured to a base assembly that is fixedly mounted to the engine header or some other fixed location.
The absence of high standards of quality control in diesel fuel supplies dictates that an effective fuel filter be incorporated into the fuel supply system of a diesel engine. It is not uncommon for diesel fuel to have significant quantities of abrasive particles and water. The abrasive particles present the potential for permanent damage to components of the fuel injection pump. The abrasive particles can also adversely affect the performance of the pump by destroying the ability of the fuel injection pump to precisely meter and deliver fuel at high pressures. The presence of water in the diesel fuel supply can cause corrosion of engine components, and during freezing conditions, can result in interruption of the fuel injection system and/or seizure of moving components. Similarly, water and particulate matter in the lubricating oil must be removed to minimize wear of engine parts.
Conventional diesel fuel delivery systems often require a heat source to prevent formation of wax crystals during cold weather conditions. One type of conventional diesel fuel delivery system includes a heating element in the fuel path of the base which warms the fuel before it enters the filter cartridge. On warm days or after sustained engine operation, substantially less heating of the fuel is required than during start-up on days when the ambient temperature is, for example, 30 degrees below zero F. Consequently, such heating elements require a positive control, either by a relatively simple thermal switch, or by a complex electronic control system.
Another type of conventional diesel fuel delivery system utilizes the return flow from the fuel injection pump to heat the fuel drawn from the fuel tank. One such conventional system utilizes a bimetallic disc which is positioned adjacent an opening which provides fluid communication between the return flow path and the fuel supply flow path into the filter element. The bimetallic disc positively engages a first seal surface in one direction of flexure to divert all of the return flow into the filter element when the return flow temperature is below a predetermined value. When the return flow temperature is above the predetermined value, the bimetallic disc flexes in the opposite direction to engage a second seal surface and thereby close the opening. This system generally requires that a check valve be positioned in the opening.